便携式高速FTIR旋转式干涉仪数值模拟仿真分析

Numerical Simulation Analysis of Portable High-Speed FTIR Rotary Interferometers

旋转式干涉仪可实现便携式傅里叶红外光谱仪的小型化设计,同时可提供高速光谱输出,但其光程差存在非线性问题。本文详细分析了便携式傅里叶转换红外光谱(FTIR)旋转式干涉仪结构,建立参考坐标系,根据几何光学原理推导了转镜转动光程差方程,并进行了数值模拟仿真分析,阐明了干涉仪光程差与转镜厚度、折射率和转角参数间的设计关系。采用无参考激光采样方式,利用多项式拟合光程差与转角的非线性关系,获得等光程差对应的时间非均匀关系,从而实现非等时间下的等光程差采样。相比等时间采样方式光程差速度的不稳定度降低为原来的1/5.3,这为转镜的速度控制提供更大不稳定裕度,同时也提高了FTIR的抗振能力。该数值模拟仿真分析结果为实现无参考激光的便携式高速FTIR的设计参数确定和优化提供数据支持和理论依据。

Rotary interferometers enable the miniaturization of portable Fourier infrared spectrometers and provide high-speed spectral output.However,their optical path difference(OPD)is nonlinear.In this paper,we analyzed the structure of a portable Fourier-transform infrared spectroscopy(FTIR)rotary interferometer in detail and built a reference coordinate system.Then,an OPD equation for the rotating mirror was deduced according to the geometrical optics principle.Numerical simulation analysis was carried out to illustrate the relationship of OPD with the thickness,refractive index,and rotation angle of the rotating mirror.In terms of sampling without reference laser,the nonlinear relation between OPD and rotation angle was fitted by polynomials to obtain the time non-uniformity corresponding to equal OPD.As a result,the sampling with equal OPD in the case of non-equal time was achieved.Compared with that of the equal-time sampling,the instability of OPD velocity was reduced to 1/5.3,which offered a greater instability margin for the speed control of the rotating mirror and also improved the vibration resistance of FTIR rotary interferometers.Our work provides data support and theoretical basis for the design parameter determination and optimization of portable high-speed FTIR rotary interferometers without reference laser.